Self-assembled monolayers of cobalt and iron phthalocyanine complexes on gold electrodes: Comparative surface electrochemistry and electrocatalytic interaction with thiols and thiocyanate

The self-assembling of the octa(hydroxyethylthio)-metallophthalocyanine {MOHETPc (M = Co and Fe)} complexes and their similar analogues, octabutylthiometallophthalocyanine {MOBTPc (M=Co and Fe)} complexes on gold electrodes are investigated. Comparative surface voltammetric insights into their distinct self-assembling properties with respect to the passivation of Faradaic processes and surface coverages, including their solution electrochemistry, suggest different orientations and non-cleavage of their C-S bonds. In the pH 2-9 range, the reversible [(MPc)-Pc-(III)(-2)](+) / [(MPc)-Pc-(II)(-2)] redox couples show potential shifts close to -59 mV / pH. ne gold electrodes modified with the SAMs of these species show electrocatalytic activity towards the oxidation of thiols (L-cysteine, homocysteine and penicillamine) and thiocyanate in acidic media with detection limits in the region of 10(-7)-10(-1) mol dm(-1). These monolayers are stable and easily reproducible.